LSP: Add support for unreachable code display

Supporting LSP clients can display lines with UNREACHABLE_CODE as faded out

Author: Meorge

modules/gdscript/gdscript_parser.cpp

@@ -2025,6 +2025,19 @@ GDScriptParser::SuiteNode *GDScriptParser::parse_suite(const String &p_context,
 
 	} while ((multiline || previous.type == GDScriptTokenizer::Token::SEMICOLON) && !check(GDScriptTokenizer::Token::DEDENT) && !lambda_ended && !is_at_end());
 
+#ifdef DEBUG_ENABLED
+	if (current_suite->unreachable_code_start) {
+		Node *unreachable_start = current_suite->unreachable_code_start;
+		Node *unreachable_end = suite->statements[suite->statements.size() - 1];
+		push_warning(
+				unreachable_start->start_line,
+				unreachable_start->start_column,
+				unreachable_end->end_line,
+				unreachable_end->end_column,
+				GDScriptWarning::UNREACHABLE_CODE,
+				current_function->identifier ? current_function->identifier->name : "<anonymous lambda>");
+	}
+#endif // DEBUG_ENABLED
 	complete_extents(suite);
 
 	if (multiline) {
@@ -2245,7 +2258,12 @@ GDScriptParser::Node *GDScriptParser::parse_statement() {
 	if (unreachable && result != nullptr) {
 		current_suite->has_unreachable_code = true;
 		if (current_function) {
-			push_warning(result, GDScriptWarning::UNREACHABLE_CODE, current_function->identifier ? current_function->identifier->name : "<anonymous lambda>");
+			// Store where the unreachable code begins for this suite,
+			// but hold off on emitting the warning until we also know where
+			// the unreachable code ends.
+			if (current_suite->unreachable_code_start == nullptr) {
+				current_suite->unreachable_code_start = result;
+			}
 		} else {
 			// TODO: Properties setters and getters with unreachable code are not being warned
 		}

modules/gdscript/gdscript_parser.h

@@ -1202,6 +1202,7 @@ class GDScriptParser {
 		FunctionNode *parent_function = nullptr;
 		IfNode *parent_if = nullptr;
 
+		Node *unreachable_code_start = nullptr;
 		bool has_return = false;
 		bool has_continue = false;
 		bool has_unreachable_code = false; // Just so warnings aren't given more than once per block.

modules/gdscript/language_server/gdscript_extend_parser.cpp

@@ -84,6 +84,10 @@ void ExtendGDScriptParser::update_diagnostics() {
 		diagnostic.message = "(" + warning.get_name() + "): " + warning.get_message();
 		diagnostic.source = "gdscript";
 
+		if (warning.code == GDScriptWarning::UNREACHABLE_CODE) {
+			diagnostic.tags.append(LSP::DiagnosticTag::Unnecessary);
+		}
+
 		GodotRange godot_range(
 				GodotPosition(warning.start_line, warning.start_column),
 				GodotPosition(warning.end_line, warning.end_column));

modules/gdscript/language_server/godot_lsp.h

@@ -731,6 +731,27 @@ static const int Information = 3;
 static const int Hint = 4;
 }; // namespace DiagnosticSeverity
 
+/**
+ * The diagnostic tags.
+ *
+ * @since 3.15.0
+ */
+namespace DiagnosticTag {
+/**
+ * Unused or unnecessary code.
+ *
+ * Clients are allowed to render diagnostics with this tag faded out
+ * instead of having an error squiggle.
+ */
+static const int Unnecessary = 1;
+/**
+ * Deprecated or obsolete code.
+ *
+ * Clients are allowed to rendered diagnostics with this tag strike through.
+ */
+static const int Deprecated = 2;
+}; // namespace DiagnosticTag
+
 /**
  * Represents a related message and source code location for a diagnostic. This should be
  * used to point to code locations that cause or related to a diagnostics, e.g when duplicating
@@ -787,6 +808,14 @@ struct Diagnostic {
 	 */
 	String message;
 
+	/**
+	 * Additional metadata about the diagnostic.
+	 *
+	 * @since 3.15.0
+	 */
+	// Note: Uses DiagnosticTag namespace values.
+	Vector<int> tags;
+
 	/**
 	 * An array of related diagnostic information, e.g. when symbol-names within
 	 * a scope collide all definitions can be marked via this property.
@@ -808,6 +837,14 @@ struct Diagnostic {
 			}
 			dict["relatedInformation"] = arr;
 		}
+		if (!tags.is_empty()) {
+			Array arr;
+			arr.resize(tags.size());
+			for (int i = 0; i < tags.size(); i++) {
+				arr[i] = tags[i];
+			}
+			dict["tags"] = arr;
+		}
 		return dict;
 	}
 };